There are not many innovations in Minecraft 1.12. Most of the improvements are related to bug fixes and expansion of addons.

Camera. A camera has been added but has been observed to malfunction.

You can crawl. This movement option has not been reported, but players have noticed that it exists. If you stand in the water and look down,
then press forward twice, the character begins to crawl.

Fixed 240 bugs. A large number of recent updates led to errors in certain cases.

Addons. The list of items added using addons has been expanded. The functional list of mob settings has been expanded.
Increased the mechanics of using new items.